The Intraregional Subway quest is the requisitory quest of the intraregional-subway system that is biregionally interlocked between the Kanto and Johto regions. This quest's completion—in addition to the regionally respective championships for the Elite Four bureaus—is required in order to use this system to travel intraregionally between Pokémon Centers.

By concomitance of the fact that it also rewards HM02 (Fly), it is also colloquially referred to as the Fly Quest; however, those who are incentivized by that reward should bear in mind that Fly has no out-of-battle usability.

Walkthroughs

Textual guide

Throughout your infant playership, you may have noticed in Pokémon Centers that the intraregional-subway systems have been inoperational; that is because they have not have had enough money to subsidize it. With an Elite Four championship, however, you have soared up the Pokémon-trainer stratum insofar that the subway-manager is willing to solicit your help to re-operationalize it.

Conferring with the subway-manager in Saffron City about your objective.

Speaking to the subway-manager

Once you have become a regional champion by defeating Kanto's Elite Four bureau, you have qualifiable access to the quest; to start it, speak to the subway-manager in Saffron City's subway station.

He will inform you that Yorkie—their most prolific sponsor—has had too many issues to tend to with his farm; resultantly, his sponsorship has been hampered, ultimately eventuating into the suspension of the subway's operationality. He notes that Yorkie resides on Route 16 and alludes that he should be spoken to regardingly.

Visiting Yorkie

Tread to Route 16; the least roundabout route thereto would be traveling westwards from Saffron City to the western terminus of Celadon City. Remember that a Bicycle is needed in order to pass through the gatehouse to Yorkie's house; Mounts, while functionally identical, are inadmissible to Cycling Roads.

Once you have passed through the gatehouse, you will find Yorkie's house—the only house within the vicinity of the route.

When you try to speak to Yorkie, he will implore for his parcel back, which he gave to his brother; he will muse over the whereabouts of him, who suspectedly would not leave Kanto.

Locating Yorkie's brother

Do note that Yorkie's brother will not be locatable until you have spoken to Yorkie for the quest's objectives; he will still be hidden, so this step will not be progressible until you have completed that quest antecedent.

Yorkie's brother will be locationally randomized for each player, as there five possible areas to find him in as outlined below:

When you speak to him, he will admit that he still has his parcel on-hand; however, he will stipulate that you must pay 50,000 in return for it. Once you have paid for it, he will whisk off to another region, leaving you with the parcel that Yorkie has yearned for.

Nocturnal Feather

Extracting the Nocturnal Feather from a toting Pidgeotto.

Return to Yorkie with his parcel. While he is gratitudinous that you have returned it, he wants you to complete another objective before he helps you proceedingly complete the quest: obtaining a Nocturnal Feather to attest your "love" for the Pidgey evolutionary line.

The item is only dropped by Pidgeotto that inhabit Route 16. While the item's drop rate is steeply improbable and thus the hunt can be resultless for a while, the following techniques can be used to facilitate the hunt for it.

Deploy a Pokémon with the Frisk ability; this will discern whether or not the wild Pidgeotto is actively holding a Nocturnal Feather, which can help you winnow down which Pidgeotto you should invest time battling at the prospect of the item.

Use item-looting moves, such as Covet and Thief, to loot the Nocturnal Feather from wild Pidgeotto (if actively holding it). Even if the Pokémon ultimately faints, the item will still be retrieved contingent that they were actively holding it.

If you wish to capture the Pidgeotto to loot the item instead, you can use non-fainting moves, such as False Swipe or Super Fang, to help maximize your chances of capturing the Pokémon without fainting it.

Once the Nocturnal Feather has been obtained, give it to Yorkie; this will complete the quest!

Video walkthrough

Rewards

Once you have completed the quest, Yorkie will immediately reward you with HM02—the encapsulating TM of Fly.

Do note that Fly is not usable outside of battle; the move exists only for its in-battle functionality, which is now infinitely teachable to compatible Pokémon with the HM device. As a byproduct of completing its rewarding quest, however, you can now use the intraregional-subway system (read below) as the closest navigational shortcut there is to it for intraregional travel.

Intraregional-subway system

After you have completed the quest, return to the subway system in Saffron City; it will now be operational, allowing you to intraregionally travel between an a select bevy of Pokémon Centers in the Kanto and Johto regions.

To use the system, travel down the staircase in operable Pokémon Centers to speak with the subway guard; therein, you will be allowed to travel to other destinational Pokémon Centers within the region for a fee of 2,500 per travel. Alternatively, you can purchase an infinite-use weekly transit pass for 100,000, thereby allowing you to costlessly board the subway, train, and ferry systems limitlessly until it expires.